Method of producing surfaces of high heat radiation



Feb. 18, 1941 E. STROHFELDT 2,232,083 b METHOD OF PRODUCING SURFACES OF HIGH HEAT RADIATION Fild Au 24, 1958.

TUBE ENVELOPE INVENTOR POI/VT METALLIC CARBIDE T w E M RY m m m Patented Feb. 18, 1 94 METHOD OF PRODUCIN G SURFACES OF 'HIGH HEAT RADIATION E l'win Strohfeldt, Berlin, Germany, asslgnor to c. Lorenz Aktiengesellschaft, Berlin-Tempelhof, Lo'renzweg, Germany, a company Application August 24, 1938, Serial No. 228,177

. In Germany'September 6, 1937 1 Claim. 01. 250-275) The present invention relates to methods of bon producing substance such as starch, sugar producing surfaces 'of high heat radiation and or similar, on a supporting body and to convert low secondaryi electron emission, particularly in these metals or oxides into corresponding carelectric discharge devices and consists in certain I bides by heat treatment in vacuum, in hydrogen 5 features of novelty which will readily be underor in any other inert gas. Furthermore, car- I! stood from the following description and be bides may also be produced by heating the correpointed out in the appended claims. sponding metals in a disperse condition in a For the purposes of securing a higher heat carbonaceous atmosphere in which case the radiation, the outer surfaces of electron ttubes, admixture of carbon in solid form may be enfor example the superficies of the anode electlrely or partially omitted. l0 trodes in transmitter and receiver tubes are pro- The above mentioned surfaces or coatings may vided'with a coating which involves higher heat according to still a further feature of the invenradiation than the metallic surface assuch. tion be produced by spraying an emulsion, for

It is also a known expedient in connection with instance in water oralcohol, by admixing a gluten l5 Braun tubes to blacken the inner wall of the which for instance may be sugar or collodion. discharge vessel by means of i a coating in order After such surface or coatinghas been produced, to avoid light deflections at this wall and in order a protecting layer may be applied thereon. It is to simultaneously prevent emission of secondary also possible to intimately unite the coating and electrons. It is a well known expedient to use the supporting body in a sinterlng process.

soot for this purpose since this substance involves Metallic coatings which are subsequently con- 20 useful optical properties. It is also possible to verted into a carbide may be applied by sprayingemploy metal oxidas for obtaining such blackenorvaporizing the metals or their corresponding ing. However, all these substances or materials compositions, or even by means of cathode sputsuffcr under the disadvantage that considerable tering. In one particular aspect the metal layer difficulties prevail on removing residual gases is applied as a solute salt such as ammonium 25 therefrom, and that these substances are vaportungstenate whereupon this layer is converted in ized or disintegrated at high temperatures. the corresponding metal oxide or metal merely It has also been proposed to employ metals, by applying heat or in a chemical reduction. such as tungsten or molybdenum in a finely dis- The surface of the supporting member may be persed condition. These metals constitute chemroughened prior to the application of the coating 30 ical composition with residual gases at relatively in order to secure'perfect sticking between these low temperatures and, moreover cause an unde- 'two members. sired emission of secondary electrons. The coating in Braun tubes may for instance According to the main feature of the present be produced in such manner that the inner sur- 15 invention, these disadvantages are obviated by face of the glass envelope is at first coated with 3 producing surfaces consisting of carbides having a thin layer of metal, such as silver'whereupon a high melting point, such as zirconium carbide, a film or layer of a carbide having a high melttungsten carbide, molybdenum carbide or simiing point is applied on the first mentioned lar metallic compositions. coating.

40 The above'mentioned metallic compositions are The single figure in the drawing illustrates a 40 characterized by their particularly high melting tube constructed in accordance with the method point andtheir extreme stability with respect to of my invention. thermical, chemical and other disintegrating What is claimed is: influences. These compositions, moreover, create A method of producing surfaces of high heat aconsiderably lower electron'emission than their radiation and low secondary emission which 45 metallic components. It is not necessary to method comprises selecting at least one carbide merely employ such carbides since it will be posfrom the group consisting of zirconium carbide, sible to use compositions of different carbides tungsten carbide, molybdenum carbide, boric caror to mix a carbide with soot or other disperse bide, and silicon carbide, emulsifying said car- 60 metals such as tungsten, molybdenum, nickel, bide in a fluid from the groupconsisting of water cobalt and so forth. and alcohol, spraying a layer of said emulsion on According to a further feature of the invena supporting surface, and coating said layer of tion it is not necessary to employ previously proemulsion with a protecting layer of collodion. duc'ed carbides since it is possible to apply the 68 metals or their oxides mixed with soot or a car- ERWIN STROHFELDT. 

